1. Field of the Invention
The present invention relates to a stage apparatus and adjustment method thereof, an exposure apparatus, and a method of manufacturing a device.
2. Description of the Related Art
Japanese Patent Laid-Open No. 10-261570 discloses a stage apparatus of the prior art, in which an angle detection mechanism is provided to an X interferometer of a laser interferometer as a measurement example of an angle (ωZ) about a Z axis of a stage. With this apparatus, X measurement light irradiated from the X interferometer is reflected by an X bar mirror of a fine moving stage of the stage, is split by a beam splitter, and is then incident on the angle detection mechanism. The angle detection mechanism detects a deviation of the X measurement light, thereby calculating a relative change in angle (ωZ) about the Z axis of the fine moving stage.
As shown in FIG. 9, at an activation timing of a stage apparatus, a position of a stage 100 is initialized. The stage 100 includes a fine moving stage 101 and coarse moving stage 102. Upon initialization of the position of the stage 100, a reference required to position the stage is calculated. The coarse moving stage 102 is pressed against three positioning pins 104 arranged on a stage base 103. In this state, a position of an X bar mirror 110 of the fine moving stage 101 is measured using X measurement light 107 of an X interferometer 106 of a laser interferometer 105. Also, a position of a Y bar mirror 111 is measured using Y measurement light 109 of a Y interferometer 108. Furthermore, initializing units 112 and 113 reset length measurement values of the X interferometer 106 and Y interferometer 108, thus calculating a reference. The positioning pins 104 are designed to set an absolute angle ωZ of the fine moving stage 101 with respect to a reference coordinate system to be zero when the coarse moving stage 102 is pressed against these pins.
However, with this method, it is not guaranteed that the positioning pins 104 are adjusted to set the absolute angle ωZ of the fine moving stage 101 to be zero with sufficiently high precision. Even when the positioning pins 104 are adjusted, a deviation occurs depending on the pressing method of the coarse moving stage 102 in the initialization method of pressing the coarse moving stage against the positioning pins, and the absolute angle ωZ of the fine moving stage 101 may not be set to be zero at sufficiently high precision. Furthermore, the positioning pins 104 may be worn due to aging. Even when the coarse moving stage 102 is pressed against the positioning pins 104 without any deviation, the fine moving stage 101 may already have an inclination in that state. As described above, even after the aforementioned initialization operation, an angle θXSZ made by the X measurement light 107 and X bar mirror 110 in the laser interferometer 105 and an angle θYSZ made by the Y measurement light 109 and Y bar mirror 111 in a laser interferometer 105 may not be 90° with sufficiently high precision. The laser interferometers 105 of the conventional stage apparatus can measure a relative change in angle ωZ of the fine moving stage 101 with respect to the stage initial state. However, the angle θXSZ made by the X measurement light 107 and X bar mirror 110 and the angle θYSZ made by the Y measurement light 109 and Y bar mirror 111 in the laser interferometers 105 cannot be detected.
In this state, when emergence angles of laser beams or the X measurement light 107 and Y measurement light 109 of the laser interferometers 105 have changed, length measurement errors occur in the laser interferometers 105. FIG. 10 shows a length measurement error of the laser interferometer 105 when the X measurement light 107 and X bar mirror 110 are not orthogonal to each other about the Z axis. Assume that an emergence angle of a laser beam 115 has changed at a laser emergence port of a laser light source 114. Let L be a distance from the laser light source 114 to the X bar mirror 110, and θSZ be an angle in a counterclockwise direction from the X measurement light 107, which is made by the X measurement light 107 and X bar mirror 110. Let ΔθL1 be a change amount, in a counterclockwise direction from the laser beam 115, of the emergence angle of the laser beam 115 about the Z axis, and ΔθL2 be a change amount in a clockwise direction. At this time, a length measurement error E of the X interferometer 106 is expressed by:E=EΔθL1+EΔθL2=L×tan(ΔθL1+ΔθL2)×tan|θSZ−π/2|  (1)where ΔθL1, ΔθL2, and (θSZ−π/2) are angles around zero. Therefore, the length measurement error E of the X interferometer is approximated by:E=L×(ΔθL1+ΔθL2)×|θSZ−π/2|  (1′)
If L=1 m, θSZ=(5×e−4+π/2) rad, and ΔθL1+ΔθL2=5e−6 rad in equation (1′), the length measurement error E=2.5 nm, and poses a problem in positioning of the stage apparatus which is required to have a nano order resolution.
A change in laser emergence angle is caused by a time change in local temperature distribution in an optical path (common path) extending from the laser light source 114 to the X interferometer 106 in the laser interferometer 105 and vibrations of optical members such as the laser light source 114 and a beam splitter. Especially, although a heat generating member such as the laser light source 114 is arranged around the common path, positive temperature management is not often made unlike in a measurement space of the position of the fine moving stage 101. For this reason, a time change in temperature distribution readily takes place around the common path, and a change in emergence angle of the laser beam 115 is more likely to occur due to refraction of light.